In assembly line manufacture, workpieces are conveyed along a path between multiple stations where operators perform sequential tasks on the workpieces. The workpieces are commonly supported on wheeled carts conveyed along the path by a drive system to which the cart is secured.
It is desirable to provide adjustability in the height at which the workpieces are supported by the carts. Adjustment in the height of a supported workpiece facilitates the performance of differing tasks on the workpiece. Such adjustment also facilitates the performance of a task by differing operators by providing for adjustments based on operator height or individual preferences, for example. It is known to include motor driven scissors-lift mechanisms for adjustment in the height of a load supporting platform. In U.S. Pat. No. 6,112,858 to Arnst (incorporated herein by reference in its entirety), actuation and control of the scissors-lift mechanism is limited to simple on-off control provided by foot-peddles carried by the base portion of the cart.
It is also desirable to provide for adjustability in the rotational orientation of a cart supported workpiece. Such adjustment in the rotational orientation facilitates the performance of tasks on opposite sides of the workpiece or for providing additional access to the workpiece, for example. In Arnst '858, a pivotably supported turntable provides for adjustment of the rotational orientation of a supported load. The adjustment in the orientation of the workpiece, however, is limited to rotational adjustment about a vertical axis (i.e., about a single axis). Also, the turntable disclosed in Arnst '858 is not motor driven. Adjustment of the rotational orientation of a supported load in Arnst, therefore, requires that the workpiece be rotated manually by an operator at a particular station on the assembly line.